In appliances which have a housing with an enclosed air volume which is exposed to temperature variations and therefore also to variations in volume, a pressure compensation element is usually provided. Such a pressure compensation element may be designed, for example, as a microporous diaphragm. Such a diaphragm is usually air-permeable.
One problem with such microporous diaphragms is that they are mostly impermeable to liquid water, but not to water vapor. In an atmosphere with high atmospheric moisture, therefore, moist air may pass through these microporous diaphragms into the housing interior. It may happen, inside the housing, that the moisture condenses out of the air to form liquid water. Such condensate may then cause the appliance to be damaged and may possibly even lead to its failure.
Attempts have already been made to capture such condensate by means of appropriate devices inside the housing and to collect it at suitable uncritical locations in the housing. In such solutions, however, the collected water remains inside the housing, so that, in course of time, very large quantities of condensate may accumulate. If the appliance is exposed to a temperature rise, the collected condensate may possibly partially evaporate again and increase the atmospheric moisture inside the housing. If the temperature then falls again, there is once again the risk that the water condenses at critical locations in the housing and causes damage.
DE 10 2007 011 026 A1 discloses a battery in which there is no microporous diaphragm provided as a pressure compensation element, but instead pressure compensation takes place via an orifice and a venting hose connected to it. In this battery, a cold trap for the collection of water is located inside the housing. The collected condensate is then discharged via an orifice and the venting hose out of the inside of the housing into the surroundings. One problem with this battery design is that the orifice and the venting hose have to be configured so as to be liquid-permeable so that the condensed water can be discharged out of the cold trap into the surroundings. On account of this, water may also enter the interior of the battery through this orifice and the venting hose, especially when the battery and therefore the cold trap are not actively in operation. Consequently, although this battery design has the possibility of transporting water out of the battery interior, this nevertheless entails an increased risk of absorbing water from the surroundings.